Masking of antigenic epitopes by antibodies shapes the humoral immune response to influenza

The immune responses to influenza, a virus that exhibits strain variation, show complex dynamics where prior immunity shapes the response to the subsequent infecting strains. Original antigenic sin (OAS) describes the observation that antibodies to the first encountered influenza strain, specifically antibodies to the epitopes on the head of influenza''s main surface glycoprotein, haemagglutinin (HA), dominate following infection with new drifted strains. OAS suggests that responses to the original strain are preferentially boosted. Recent studies also show limited boosting of the antibodies to conserved epitopes on the stem of HA, which are attractive targets for a ‘universal vaccine’. We develop multi-epitope models to explore how pre-existing immunity modulates the immune response to new strains following immunization. Our models suggest that the masking of antigenic epitopes by antibodies may play an important role in describing the complex dynamics of OAS and limited boosting of antibodies to the stem of HA. Analysis of recently published data confirms model predictions for how pre-existing antibodies to an epitope on HA decrease the magnitude of boosting of the antibody response to this epitope following immunization. We explore strategies for boosting of antibodies to conserved epitopes and generating broadly protective immunity to multiple strains.     

Regulation of the immune response to polyvinylpyrrolidone: Effect of antilymphocyte serum on the response of normal and nude mice

The plaque-forming cell (PFC) responses of normal and congenitally thymus-deficient (nude) mice to polyvinylpyrrolidone (PVP) were compared. Normal and nude mice responded similarly to an optimally immunogenic dose of PVP. Antithymocyte serum or antilymphocyte serum treatment of immunized mice caused a five to 10-fold increase in the PVP-specific PFC response in normal mice; the response in nude mice was not increased by such treatment.The data suggest that, although thymus-derived cells are not an absolute requirement in the immune response to PVP, these cells can regulate the magnitude of the immune response to this antigen.     

The differential effects of PGE on the immune response in normal and immunosuppressed mice

The effect of 16,16-dimethyl-PGE₂-methyl ester (di-M-PGE₂) on humoral and cellular immunoresponsiveness has been compared in normal mice and in mice immunosuppressed by splenectomy and thymectomy plus antithymocyte serum (ATS). Splenectomy resulted in immunosuppression manifested by augmentation of B-16 melanoma growth; this stimulatory effect was reversed by di-M-PGE₂. In animals immunosuppressed by thymectomy plus ATS, di-M-PGE₂ augmented the humoral and cellular immune responses; this was manifested by slowing of the growth of B-16 melanoma and by stimulating the number of plaque-forming cells, hemagglutinin titers, and delayed-hypersensitivity reactions to sheep erythrocytes. In contrast, in normal (nonthymectomized) mice, di-M-PGE₂ was mildly immunosuppressive. Finally, adriamycin-immunosuppressed normal mice and this suppression were reversed by the addition of di-M-PGE₂ to the treatment regimen.     

Evolution of preproinsulin gene in birds

The coding region of the preproinsulin gene has been cloned and partly sequenced in a variety of marine and terrestrial birds (28 species). All genes showed the "ancestral" structure with a large intron-2. The size of intron-2 changed considerably during the evolution of birds (2.4-4.2kb). The hydrophobicity of signal peptides was conserved. Bird C-peptides were predicted to be 28 amino acids long, but circulating C-peptides would be only 26 amino acids long, with Passer as a possible exception. Bird C-peptides were found to lack the sequences identified in mammals as responsible for peptide bioactivity and the structure of the central part. In contrast, predicted insulin sequences were highly conserved. Only two types of analog were identified: the hypoactive form (GluA8), present only in Anseriformes and the hyperactive form (His A8), present in all other species. Based on 3'-nucleotide sequence analysis (extending into intron-2), birds appeared to be monophyletic. Five groups were clearly identified: Paleognathae, Galliformes, Anseriformes, Passeriformes, and Charadriiformes. Paleognathae were suggested as the basal group, supporting the traditional view of avian evolution. Subsequent branching identified a gallo-anserae group and a group containing all other Neognathae. Surprisingly, Columba livia (Columbiforme order) clustered with Galliformes. With represented species, Procellariiformes and possibly Ciconiiformes, and Pelicaniformes were suggested as paraphyletic, in agreement with conclusions from some studies based on mitochondrial DNA sequences.     

OsRboh基因家族在水稻免疫应答中的表达及功能分析

为了阐明Rboh基因家族在水稻免疫应答中的功能,首先利用生物信息学方法从水稻基因组数据库中检索到7个水稻Rboh基因,并对其进行系统发育学和组织特异性表达分析,发现OsRbohD只在穗和愈伤组织中表达,且OsRbohE和OsRbohF仅在愈伤组织中特异表达,而其他基因为组成型表达。利用Real-time PCR对分别在水杨酸SA、茉莉酸甲酯MeJA和水稻黄单胞菌PXO99致病菌株处理下的OsRboh基因家族的表达水平进行了分析,同时对处理后的叶片H2O2含量进行测定。结果表明,SA可以提高OsRbohA、OsRbohB、OsRbohC和OsRbohD的表达水平,MeJA可以提高OsRbohA、OsRbohB、OsRbohC和OsRbohG的表达水平,接种水稻黄单胞菌致病菌株PXO99可以提高OsRbohA和OsRbohB的表达水平。然而三者在诱导OsRboh基因家族成员的表达时序性和表达程度存在着差异。此外,3种不同处理都能导致不同程度的H2O2积累。结果显示,OsRboh基因家族各基因在水稻免疫应答中可能扮演不同角色,发挥不同作用。     

Multigenic regulation of the primary immune response to ovalbumin in mice

At least four genes regulate the primary immune response to ovalbumin in mice. The ability to be sensitized to transfer delayed type hypersensitivity to ovalbumin is controlled by two genes. One gene,OVA-, is linked to theH-2 complex and maps to the left ofI-E. The linkage of the other gene,OVA-Bg1, has not been determined, but it segregates independently of theLy M locus, of the heavy chain allotype genes and of certain genes controlling coat color. At least two genes regulate the ability to respond with a primary antiovalbumin antibody response. One gene,OVA-, is linked to theH-2 complex and maps to the right ofI-E. Discordance of the minimum dose of antigen needed to elicit delayed type hypersensitivity response and antibody suggests that non-H-2 gene(s) regulating the primary antibody response are different fromOVA-Bg1.Abbreviations used in this paper BSA bovine serum albumin - DTH delayed type hypersensitivity - H-2 major histocompatibility complex of mouse - Ir gene — immune response gene - OVA ovalbumin - SRBC sheep red blood cells     

Local immune response in mice to Vibrio cholerae.

Cholera immunization schedules were investigated in mice, with emphasis placed on obtaining an immune response in the intestine. The most effective schedule for producing a good local response was found to be several orally-given priming doses of the organism followed after 14 days by an intravenous boosting dose. Major differences between the immune responses in the spleen and the intestine were noted.     

T cell response to preproinsulin I and II in the nonobese diabetic mouse

Immunization against insulin, insulin B chain, or B chain peptide B(9-23) (preproinsulin peptide II(33-47)) prevents diabetes in the nonobese diabetic (NOD) mouse. Whether or not peptide II(33-47) is the only proinsulin determinant recognized by CD4 T cells remains unclear. Using two peptide libraries spanning the entire sequence of preproinsulin I and preproinsulin II, respectively, we identified T cells specific for four proinsulin epitopes within the islet cell infiltrate of prediabetic female NOD mice. These epitopes were among immunogenic epitopes to which a T cell response was detected after immunization of NOD mice with individual peptides in CFA. Immunogenic epitopes were found on both isoforms of insulin, especially proinsulin II, which is the isoform expressed in the thymus. The autoimmune response to proinsulin represented only part of the immune response to islet cells within the islet cell infiltrate in 15-wk-old NOD mice. This is the first systematic study of preproinsulin T cell epitopes in the NOD mouse model.     

Involvement of the virulence gene products of Yersinia enterocolitica in the immune response of infected mice

The virulence of Yersinia enterocolitica is known to be highly dependent on its virulence plasmid. However, it remains unclear whether the virulence plasmid is engaged also in the induction of cell-mediated immunity that is essential for protective immunity in the host. In this study, we have compared the induction of type 1 helper T cell immunity against Y. enterocolitica using a virulent strain (P+) harboring the pYV plasmid and an avirulent strain (P-) harboring no pYV. Spleen cells from both groups of mice immunized with 1/10 LD50 of P+ strain and those with 1/10 LD50 of P- strain produced a high level of gamma interferon (IFN-gamma) upon stimulation with heat-killed bacteria, and CD4+ T cells were exclusively responsible for IFN-gamma production. When crude Yersinia outer proteins (Yops) were used for antigenic stimulation, IFN-gamma response of immune spleen cells against crude Yops was observed only in mice immunized with P+ strain. Flowcytometric analysis revealed a significant level of increase in IFN-gamma-producing CD8+ T cells as well as the increase in IFN-gamma-producing CD4+ T cells against crude Yops. These results suggest that the virulence plasmid of Y. enterocolitica is involved in the induction of Th1-type of possibly protective T cells in infected mice.     

Suppression of the immune response to Trichuris muris in lactating mice.

Mice infected with Trichuris muris during lactation were unable to expel the infection at the normal time, but expulsion occurred when lactation was terminated. Suppression of expulsion was uniform in mice suckling more than five young but variable with smaller litters. Mice exposed to a primary infection while lactating were shown to have serum antibodies capable of passively transferring immunity to recipient mice and showed near normal immunity to a secondary infection given after lactation had ceased. Acquired immunity to T. muris was also suppressed by lactation, but the worms which became established in lactating resistant mice were fewer and smaller than those in non-lactating, non-resistant controls. It is suggested that the suppressive effect of lactation in this host-parasite relationship is exerted on the second, lymphoid cell-mediated phase of worm expulsion.     

Expression of Helicobacter pylori cag12 gene in Lactococcus lactis MG1363 and its oral administration to induce systemic anti-Cag12 immune response in mice

To develop an oral vaccine against Helicobacter pylori infection, we have expressed the H. pylori cag12 (HP0532) gene, encoding the outer membrane protein Cag12 (31 kDa), in a live delivery vehicle Lactococcus lactis. The cag12 gene was amplified by polymerase chain reaction (PCR) using the genomic DNA of H. pylori K51 isolated from Korean patients. DNA sequence analysis revealed that the cag12 gene of H. pylori K51 has 98.1 and 97.4% identity with individual cag12 genes of the H. pylori 26695 and J99, respectively. The GST–Cag12 fusion protein, produced using the Escherichia coli expression system, was used to raise a rat polyclonal anti-Cag12 antibody. The PCR-amplified cag12 gene of H. pylori K51 was cloned in the E. coli–L. lactis shuttle vector (pMG36e) and transformed into L. lactis. Western blot analysis demonstrated that the Cag12 protein was expressed in the L. lactis transformant, with a maximum level at the log phase without extracelluar secretion. The oral administration of the transformant into mice resulted in the generation of the anti-Cag12 antibody in serum in two out of five cases. These results suggest that the recombinant L. lactis, which expresses Cag12, may be applicable as an oral vaccine to induce protective immunity against H. pylori.     

A CpG oligodeoxynucleotide enhances the immune response to rabies vaccination in mice

Background

Rabies is a fatal disease that is preventable when post exposure prophylaxis (PEP) is administered in a timely fashion. CpG oligodeoxynucleotides (ODNs) can trigger cells that express Toll-like receptor 9, and their immunopotentiation activity in an inactivated aluminum-adjuvanted rabies vaccine for dogs has been identified using mouse and dog models.

Methods

A human diploid cell rabies vaccine (HDCV) of humans and a CpG ODNs with cross-immunostimulatory activity in humans and mice were used to evaluate the immunogenicity and protective efficacy of CpG ODN in a mouse model that simulates human PEP.

Results

HDCV combined with CpG ODN (HDCV–CpG) stimulated mice to produce rabies virus-specific neutralizing antibody (RVNA) earlier and increased the seroconversion rate. Compared with HDCV alone, either HDCV–1.25 μg CpG or HDCV–5 μg CpG increased the levels of RVNA. In particular, 5 μg CpG ODN per mouse significantly boosted the levels of RVNA compared with HDCV alone. IFN-γ producing splenocytes generated in the HDCV-5 μg CpG group were significantly increased compared to the group treated with HDCV alone. When the immunization regimen was reduced to three injections or the dose was reduced to half of the recommended HDCV combined with CpG ODN, the RVNA titers were still higher than those induced by HDCV alone. After viral challenge, 50% of mice immunized with a half-dose HDCV–CpG survived, while the survival rate of mice immunized with HDCV alone was 30%.

Conclusions

The immunopotentiation activity of CpG ODNs for a commercially available human rabies vaccine was first evaluated in a mouse model on the basis of the Essen regimen. Our results suggest that the CpG ODN used in this study is a potential adjuvant to rabies vaccines for human use.

     

Effect of neutrophilokines on the immune response in mice

The influence of different peptide fractions obtained from the intact and latex-stimulated neutrophils on the immune response was studied. It was demonstrated that neutrophils after stimulation synthesize the factors activating immune response, the intact neutrophils synthesize the suppressor factors of peptide nature.